The present invention generally relates to dictating machines having a revising function, and more particularly to a dictating machine which records a correction signal onto a magnetic tape in superimposition with an originally recorded content when correcting the originally recorded content or adding a content to the originally recorded content so as to accurately indicate a position where the correction or the addition is required, without erasing the originally recorded content, and which is capable of recording a new content onto the magnetic tape with a large degree of freedom without erasing the originally recorded content.
Generally, a dictating machine is used to record a message onto a magnetic tape. When recording a plurality of messages by the dictating machine, it is desirable that two subsequent messages are clearly distinguishable upon reproduction. Accordingly, there was a conventional dictating machine which recorded a stop signal called a letter-end-marker and the like, between the two subsequent messages. Such a stop signal was recorded when a recording operator pushed a push-button switch when the recording of a message was completed. When this push-button switch was pushed, a stop signal oscillator operated for a predetermined time, and a signal of 40 Hz, for example, was produced for approximately 2.5 seconds.
When playing the tape which has been recorded with the messages in the dictating machine, the tape is caused to travel at a tape speed which is identical to the tape speed at the time of the recording. In a case where a typist is a playing operator, for example, the typist types the message which is reproduced from the tape. When one message among a plurality of messages is to be reproduced, a predetermined recorded position of this one message can be searched, by causing the tape to travel at a tape speed which is higher than the tape speed at the time of the recording and counting the number of stop signals which are reproduced.
Further, there was a conventional dictating machine which was designed to record an instruction signal called an insertion-marker and the like, in addition to the above stop signal. This instruction signal was recorded when the recording operator wanted to record instructions intended for the typist and the like. The instruction was recorded immediately after the instruction signal. Accordingly, when the instruction signal was reproduced at the time of reproduction, the typist listened to the instructions which followed, and typed the message which followed the instructions in accordance with the instructions.
There are times when the recording operator decides to correct a recorded content of the message or add a content to the recorded content of the message, after the message has been recorded. When correcting the recorded content of the message in the conventional dictating machine, a tape counter and the like was used to find the part on the tape where the correction was required. A new content which was to replace the originally recorded content of the message, was then recorded from the above part which has been found. The originally recorded content of the message was erased as the new content was recorded.
However, according to the above correcting method, it was technically difficult to accurately replace only the content in the message which required the correction with the new content. That is, a part of the recorded content which was actually required was sometimes erased erroneously, and a part of the recorded content which was actually not required was sometimes left unerased. Especially when the required recorded content was erased erroneously, it became necessary to record all of the contents of the message all over again from the beginning of the message. On the other hand, when the unrequired recorded content was left unerased, the newly recorded content did not connect smoothly to the subsequent recorded content, and in some cases, the typist was unable to correctly understand the recorded contents of the message.
When the content which required the correction was recorded over a predetermined length of tape, and the length of tape which was required to record the new content was smaller than the above predetermined length, it was possible to record all of the new content, however, a part of the unrequired content was inevitably left unerased. On the other hand, when the length of tape which was required to record the new content was greater than the above predetermined length, it was impossible to record all of the new content. Hence, in this case, there was a disadvantage in that it was impossible to correct only the unrequired content in the message, and for this reason, the same message including the new content had to be recorded all over again from the beginning of the message. Moreover, when adding a new content to the recorded content in the message, it was impossible to record the new content unless the same message including the newly added content was recorded all over again from the beginning of the message.